The Padres took over the National League lead in one truly offensive category Monday night.

Pittsburgh starter Francisco Liriano struck out 13 Padres in seven shutout innings and two Pirates relievers added four more in a pair of innings as the Pirates defeated the Padres 3-1 before 24,850 at Petco Park.

The 17 strikeouts raised the Padres total for the season to a league-leading 1,069. Only one team in the major leagues - the Houston Astros - has fanned more than the Padres.

And the trend is toward more strikeouts.

After five games of their season-long, 10-game homestand, the Padres have struck out 59 times in 46 innings – including 45 times in their three losses.

Liriano had eight strikeouts over the first three innings and once struck out four straight Padres.

“I think Liriano’s mix of pitches was as good as we’ve seen all year,” said Padres manager Bud Black. “His slider had tight rotation. Out of the hand it looks like a strike, then it disappears.”

Will Venable, whose career-best 15-game hitting streak ended Monday night, struck out three times. So did Jedd Gyorko, while Chris Denorfia, Chase Headley and Andrew Cashner all struck out twice.

The 17 strikeouts, however, was not a season high. Eighteen Padres struck out on May 10 in a nine-inning game at Tampa Bay.

“The swings with two strikes are not as short as they need to be,” said Black. “We’re expanding the zone with two strikes. You can’t hit like that.”

The Bucs took a 2-0 lead in the fourth on a three-base error by right fielder Denorfia and added a third run in the sixth on Pedro Alvarez’s National League-leading 31st homer.

In the fourth, Alvarez followed Andrew McCutchen’s lead-off single with a single to right center.

As he charged the ball with an eye on making a play on McCutchen at third, Denorfia ran right past the ball, which rolled to the right field fence – the three-base error allowing both McCutchen and Alvarez to score.

“I just missed it,” said Denorfia, who hadn’t made an error since making two in the same game on June 24. “There’s really no excuse for it. It cost us the game. I am humbled for it.”

The Padres got on the board in the ninth on a single by Headley and a two-out double by Nick Hundley.

Ironically, the Padres are hitting .278 over the first five games of the homestand. But they are hitting .398 over the past five games when they put the ball into play.

Fifty-nine of the Padres 129 outs on their homestand have come via the strikeout.

Liriano, whom the Pirates signed as a free agent in February, allowed four hits and faced Padres with runners in scoring position in only two innings while improving to 14-5.

Padres starter Andrew Cashner allowed three runs (one earned) on five hits and two walks in seven innings.

“It's like with any error, just tough luck,” Cashner said of Denorfia’s error. “I’ve got to make better pitches when we’re facing a guy like Liriano.”